Which of the following compounds containing a carbonyl group will give a coloured crystalline compound with $2, 4-DNP$?

An organic compound $(A)$ with molecular formula $C_8H_8O$ forms an orange-red precipitate with $2,4-DNP$ reagent and gives a yellow precipitate on heating with iodine in the presence of sodium hydroxide. It neither reduces Tollens' or Fehlings' reagent,nor does it decolourise bromine water or Baeyer's reagent. On drastic oxidation with chromic acid,it gives a carboxylic acid $(B)$ having molecular formula $C_7H_6O_2$. Identify the compounds $(A)$ and $(B)$ and explain the reactions involved.

Toluene $\xrightarrow[(2) \ H_3O^{+}]{(1) \ CrO_2Cl_2 / CS_2} X$ $\xrightarrow{\text{Conc. } NaOH} Y + Z$. The correct statements about $Y$ and $Z$ are:
$A. \quad Y$ is a secondary alcohol
$B. \quad Y$ is the reduction product of $X$
$C. \quad Z$ on heating with soda lime gives benzene
$D. \quad Y$ does not give $H_2$ gas with $Na$ metal

In the given reaction sequence,the conversion of $B$ to $C$ is known as:

To distinguish between formaldehyde and acetaldehyde,we require

In the given reaction,what will be $A$ and $B$ respectively?
$(CH_3)_2CO$ $\xrightarrow{NaCN/HCl} A$ $\xrightarrow{H_3O^+} B$